When mystery-thriller writer Richard Castle (Nathan Fillion) is called in to help investigate a series of copycat murders based on his books, he finds he enjoys the experience sufficiently to want to continue it. Pulling strings, he arranges to accompany NYPD Detective Kate Beckett (Stana Katic), claiming he wants to study and use her as a personality basis for his next book series. But their personalities don't mesh -- Castle's fly-by-the-seat-of-his-pants detective style greatly clashes with Beckett's more conservative and methodical approach to the crimes, but the new life that Castle has begun couldn't have been scripted better by himself.